Hardcoded /login URLs do not work with FORCE_SCRIPT_NAME

When the mooc-grader installation uses the FORCE_SCRIPT_NAME Django setting to serve all mooc-grader views behind a common URL prefix, then the system breaks down due to the hardcoded /login URL in a couple of places. The code should use the Django URL resolvers to form the URLs instead of hardcoding the URL strings.

This affects Tampere University since they use FORCE_SCRIPT_NAME. Their graders are supposed to be served from URL paths starting /graderA, on another server /graderE and so on. The prefix should affect all URLs of the MOOC-Grader. The URL path prefix is needed when the URL domain name is shared between multiple servers.

Hardcoded /login is used here:

mooc-grader/util/auth.py

Line 11 in 1f5b163

    
           login_required: Callable[[ViewType],ViewType] = login_required_base(redirect_url="/login?referer={url}")

When Tampere hardcodes login_required_base(redirect_url="/graderA/login?referer={url}") there, it works.
Note that reverse() doesn't seem to work in the module-level code since Django has not set up everything when the module is loaded and the module-level code is executed.
https://docs.djangoproject.com/en/3.2/ref/urlresolvers/#reverse

mooc-grader/access/templates/access/login.html

Line 20 in 1f5b163

xml.open("POST", "/login");

Aalto internal ticket:
https://rt.cs.aalto.fi/Ticket/Display.html?id=21827

At least, fixing the template should be trivial since it can use the normal url template tag:

mooc-grader/access/templates/access/login.html

Line 20 in 1f5b163

xml.open("POST", "/login");

https://docs.djangoproject.com/en/3.2/ref/templates/builtins/#url